Improved electrodes for energy storage devices

Abstract

Electrodes having associated therewith a protective porous film or coating of boron nitride nanotubes (BNNTs).

1 . A metal electrode for an energy storage device having a composite of boron nitride nanotubes (BNNTs) and at least one polymeric binder, wherein a coating of the composite intimately contacts at least one surface of the electrode as a porous mesh which is selectively permeable to transport metal ions used in the energy storage device, wherein the composite is physically and/or chemically bonded to the surface of the electrode. 
     
     
         2 . The electrode of  claim 1 , wherein the mesh is configured to homogeneously distributes metal transport ions traversing the mesh across an entire surface of the metal electrode thereby reducing metal dendrite formation. 
     
     
         3 . The electrode of  claim 1 , wherein at least a portion of the polymer binder is present as particulates which fix strands of the BNNTs together to form the porous network or porous mesh. 
     
     
         4 . (canceled) 
     
     
         5 . The electrode of  claim 1 , wherein strands of BNNTs are not completely conformally coated with the polymeric binder. 
     
     
         6 . The electrode of  claim 1 , wherein the BNNTs are substantially free, preferably completely free, of impurities hexagonal boron nitride and/or elemental boron. 
     
     
         7 . The electrode of  claim 1 , wherein the metal is selected from Li, Na, K, Al, and Zn. 
     
     
         8 . The electrode of  claim 1 , wherein the coating of the composite comprises the polymeric binder at a concentration of about 50 wt % or less, preferably 20 wt % or less, preferably 15 wt % or less, preferably about 10 wt % or less. 
     
     
         9 . The electrode of  claim 1 , wherein the BNNT porous mesh comprises one or more of tunnels, pathways and/or channels therethrough, directed, orientated and/or dimensioned to delocalised or redistribute a concentrated metal ion flux on one side of the mesh to a more uniformly distributed metal ion flux on the other side of the porous network/mesh, whereby the metal ion flux is thereby distributed across a greater surface area of the electrode. 
     
     
         10 . The electrode of  claim 1 , wherein the composite has an average thickness of from about 1 micron to about 50 microns. 
     
     
         11 . The electrode of  claim 1 , wherein the coating of the composite has an areal density or BNNT loading of from about 0.2 mg cm −2  to about 8 mg cm −2 . 
     
     
         12 . The electrode of  claim 1 , wherein the polymeric binder is selected from styrene butadiene rubber, poly(vinylidene fluoride-co-hexafluoropropene (PVDF-HFP), poly(3,4-ethylenedioxythiophene)-co-poly(ethyleneglycol) (PEDOT-co-PEG), polyethylene glycol (PEG)-polymethyl methacrylate (PMMA), poly (dimethylsiloxane) (PDMS) and combinations thereof. 
     
     
         13 . The electrode of  claim 1 , wherein the metal electrode is deposited on a current collector which is selected from carbon cloth, carbon fibre, copper foam, nickel foam, and copper foil. 
     
     
         14 - 26 . (canceled) 
     
     
         27 . The electrode of  claim 1 , wherein the metal is selected from Li or Na. 
     
     
         28 . The electrode of  claim 10 , wherein the composite has an average thickness of from about 2 microns to about 25 microns. 
     
     
         29 . The electrode of  claim 10 , wherein the composite has an average thickness of from about 3 microns to about 10 microns. 
     
     
         30 . The electrode of  claim 10 , wherein the composite has an average thickness of from about 1.5 microns to about 7.5 microns, or about 5 microns. 
     
     
         31 . The electrode of  claim 10 , wherein the coating of the composite has an areal density or BNNT loading of from about 0.1 mg cm −2  to about 2 mg cm −2 . 
     
     
         32 . The electrode of  claim 10 , wherein the coating of the composite has an areal density or BNNT loading of about 0.4 mg cm −2 . 
     
     
         33 . The electrode of  claim 1 , wherein the polymeric binder is a flexible polymeric binder comprising poly(styrene-co-butadiene). 
     
     
         34 . A negative electrode (anode) for an energy storage device, comprising a metallic based anode material, the negative electrode having associated therewith boron nitride nanotubes (BNNTs) in the form of one or more deposits or interlayers of BNNTs having a porous mesh structure.